1. Field of the Invention
The present invention relates to polymer particles, and more particularly to polymer resin particles which are suitable as a component of the dry-type toners which are used in copiers, printers, plotters and facsimile machines.
2. Description of the Related Art
Polymer resin particles are being manufactured using such methods as emulsion polymerization, seed polymerization, suspension polymerization and dispersion polymerization, and they are being used in various fields such as binders for toners, cosmetics, column chromatography and spacers for liquid crystal displays.
A particle size within the range from a few xcexcm to a few tens of xcexcm is required when polymer resin particles are to be used as a binder for a toner and, since the particle size is too small with a single polymerization using the emulsion polymerization method or the seed polymerization method, the polymerization has to be carried out repetitively, and this inevitably results in longer times and increased cost. Furthermore, although particles of a size ranging from a few xcexcm to a few tens of xcexcm can be obtained if the suspension polymerization method is used, in this case the particle size distribution is wide and there is pronounced variability, and aggregation and fusion are liable to occur in high temperature, high humidity environments.
Conventionally, particle size has been controlled by adjusting the amount of monomer or initiator so as to obtain the required particle size. However, if the particle size is increased using these methods of adjustment then the molecular weight is inevitably reduced at the same time and so it is difficult to produce polymer resin particles which have a large particle size and a high molecular weight.
It is easy to produce particles which have a comparatively uniform particle size in particular by using dispersion polymerization, but there is a problem in that the molecular weight falls when large particles are formed. If the molecular weight is low then the particles are liable to condense and this results in problems with a deterioration of image quality.
Hence, for use as a toner binder, the polymer particles must have a particle size from a few xcexcm to a few tens of xcexcm, the particle size must be uniform, and the particles must have a suitable molecular weight. However, polymer particles which satisfy these requirements cannot be manufactured cheaply and efficiently using the conventional methods.
A first object of the present invention is to provide polymer resin particles which have a comparatively large and uniform particle size which can be manufactured efficiently and cheaply. A second object of the present invention is to provide a toner which is cheap and has excellent performance.
According to a first aspect of the present invention there are provided polymer resin particles which are obtained by the dispersion polymerization of monomer which contains organosilane compound. In this invention, the variability of the particle size of the polymer resin particles which are obtained by the dispersion polymerization of monomer is small because organosilane compound is contained in the monomer which is used for the dispersion polymerization. For example, a degree of dispersion of not more than 1.3 can be obtained. Furthermore, polymer resin particles of which the content of particles at least 1.5 times the volume average particle size is not more than 5% and the content of particles not more than 0.9 times the number average particle size is not more than 20% can be obtained.
The polymer resin particles of the present invention can have a comparatively large particle size, for example a volume average particle size of from 4 to 10 xcexcm, and a sufficient molecular weight, which is to say a weight average molecular weight of from 10,000 to 100,000. Hence the polymer resin particles of this invention are especially suitable as binder resins for the dry-type toners which are used for high image quality printing since they have simultaneously a suitable particle size distribution, a large particle size, and a sufficient molecular weight.
In the polymer resin particles of the present invention, styrene may be used as monomer, for example, from 70 to 90 wt % of the monomer. Moreover, the monomer may contain acrylic acid ester or methacrylic acid ester in addition to styrene. The monomer can contain from 1 to 5 wt % organosilane.
According to a second embodiment of the present invention there is provided a method for the manufacture of polymer resin particles comprising adding monomer which contains organosilane compound to a solvent which contains dispersing agent and dispersion-polymerizing the monomer which contains the organosilane compound. It is possible by using the method of the present invention to manufacture efficiently and cheaply polymer resin particles which have simultaneously a suitable particle size distribution, a large particle size, and a sufficient molecular weight.
According to a third embodiment of the present invention, there is provided a toner comprising polymer resin particles as binder resin, obtained by the dispersion polymerization of monomer which contains organosilane compound, and a colorant. The toner may also contain an electrostatic charge controlling agent. A toner of the present invention ensures high-density printing with high image quality since it has a resin binder which has simultaneously a suitable particle size distribution, a large particle size, and a sufficient molecular weight.